The accuracy of forensic dental identification is without question. With their being 32 natural teeth in the adult human (counting wisdom teeth), and with each tooth having 5 separate sides, the number of possibilities of fillings on each of the surfaces of every tooth is practically unlimited. That fact, plus the durability of the human tooth to withstand fire, heat, cold, and time makes it a valuable piece of evidence that seemingly will not go away.
There are a few basic points in forensic dental identification that should be explained. First, we are comparing the shape, contour, filling type and location as presented by ‘before death’ or antemortem xrays to those taken on the body whose identity is in question. What we are looking for basically is an inexplainable inconsistency. For example if tooth #30 has a silver filling located on 4 out of the 5 surfaces as seen on the antemortem records, AND your xray from the unknown shows that # 30 is a virgin tooth with no previous dental treatment having ever been performed, THEN you can immediately exclude that person from the identity pool of possibilities.
The basic premise that this theory operates under is the fact that once a filling is placed in one or more surfaces of a tooth, you can NEVER go back in and unfill that tooth. If the situation showed a virgin tooth on the antemortem xray of #30, and the postmortem xray shows a large filling covering 3/5 surfaces of the tooth, what conclusion can you draw from that opposite scenario? The answer is NO CONCLUSION. The reason for this is because in the second example, there would be many opportunities for the victim to have gone to a dentist AFTER those xrays were taken and had a filling placed. That would result in the antemortem xrays not being consistent with the postmortem xrays.
Another point that should be taken into consideration is that of the actual composition of the filling material. These materials now can be made of silver amalgam, a mixture of multiple types of metals, gold, porcelain, or even composite resin. Each of these materials has a slightly different appearance when examined on xray. To further complicate the process, some composite resins are radiopaque (show up white on xray) while others are radiolucent (show up dark on xray). For some reason, the dental materials industry has never reached a consensus of opinion on exactly what these fillings should really look like on xray.
Silver fillings composed 90% of all dental fillings until around the 1980’s. With the ever increasing popularity of tooth colored fillings, the entire science of dental identification became more complex. Not only did the dentist have to notice which surfaces had a filling and which ones did not, he also had to note which type of material each tooth was restored with.
When a forensic dentist encounters some inexplainable inconsistencies, he/she might want to consider the possibilities that the antemortem dental records, if taken from the clinical notes rather than xray, could be human error by the original dentist. Likewise, if you have any dental xray that is not labeled, or improperly labeled, then the accuracy of the xrays could be blamed for a misidentification.
And that, my forensic lovers, should NEVER happen!